Amyloid diseases or amyloidoses include a number of disease states having a wide variety of outward symptoms. These disorders have in common the presence of abnormal extracellular deposits of protein fibrils, known as “amyloid fibrils”, “amyloid deposits” or “amyloid plaques” that are usually about 10-100 nm in diameter and are localized to specific organs or tissue regions. Such plaques are composed primarily of a naturally occurring soluble protein or peptide. These insoluble deposits are composed of generally lateral aggregates of fibrils that are approximately 10-15 nm in diameter. Though diverse in their occurrence, all amyloid deposits have common morphologic properties, stain with specific dyes (e.g. Thioflavin T, Congo red), and have a characteristic red-green birefringent appearance in polarized light after staining.
Amyloid-related diseases are characterized by the type of protein present in the deposit. For example, neurodegenerative diseases such as scrapie, bovine spongiform encephalitis, Creutzfeldt-Jakob disease and the like are characterized by the appearance and accumulation of a protease-resistant form of a prion protein (referred to as AScr or PrP-27) in the central nervous system. Similarly, Alzheimer's disease, another neurodegenerative disorder, is characterized by the deposition of amyloid plaques and neurofibrillary tangles. In this case, the plaque and blood vessel amyloid is formed by the deposition of fibrillar amyloid beta protein. Other diseases such as adult-onset diabetes (Type 11 diabetes) are characterized by the localized accumulation of amyloid in the pancreas.
Each amyloidogenic protein has the ability to fold into beta-sheets and to form insoluble fibrils, which get deposited extracellularly or intracellularly. Each amyloidogenic protein, although different in amino acid sequence, has the same property of forming fibrils and binding to other elements such as proteoglycan, amyloid P and complement component. Moreover, each amyloidogenic protein has amino acid sequences, which, although different, can catalyze the formation of beta-sheet cells. As per example, the amyloid beta fibrils have been associated with dead neuronal cells and microgliosis in patients with Alzheimer's disease. When tested in vitro, the amyloid beta peptide was shown to be capable of triggering an activation process of microglia (brain macrophages), which would explain the presence of microgliosis and brain inflammation found in the brain of patients with Alzheimer's disease.
In another type of amyloidosis seen in patients with Type II diabetes, the amyloidogenic protein IAPP has been shown to induce beta-islet cell toxicity in vitro. Hence, appearance of IAPP fibrils in the pancreas of Type II diabetic patients could contribute to the loss of the beta islet cells (Langerhans) and organ dysfunction.
One of the most prominent amyloid diseases is Alzheimer's disease, which is a progressive neurodegenerative disease affecting approximately 0.5-1% of the total population in the western world. Alzheimer's disease is characterized by the deposition of large numbers of amyloid plaques in the brain. This deposition is assumed to cause the pathology of the disease and most approaches to prevent Alzheimer's disease is aimed at reducing, removing, or preventing the formation of amyloid plaques. The main constituent of the amyloid plaques is the amyloid beta peptide (Aβ), a 40-42 amino-acid protein that is produced through cleavage of the amyloid precursor protein (APP)
The patent application US20070172496 discloses conjugates comprising the Aβ(33-42) peptide, a peptide recognized by a monoclonal antibody and albumin which are used as capture antigens in ELISA assays for determining the presence of anti-Aβ antibodies in a sample from a patient who has been immunized with a complex formed by different peptides derived from Aβ(1-42) peptide and so called ligand-presenting assembly o LPA.
Thus, there is a need in the art for additional immunogenic compositions capable of inducing an effective and sustained decreased in plasma amyloid levels and to reduce the number of amyloid deposits.